Various types of protective covers have been developed for covering piles or mounds of particulate material, such as salt, sand, grain and the like, from the effects of the weather while the material is in outside storage. An example of a cover for protecting a large quantity of particulate material from the elements when stored outside in an otherwise unprotected condition is disclosed in Handwerker U.S. Pat. No. 4,413,029. Alternately, covers comprising all porous or all non-porous materials can be utilized.
While the cover disclosed in the Handwerker patent is capable of protecting the pile or mound of material covered thereby, it possessed a number of shortcomings. For example, in order to counteract the effects of aerodynamic lift exerted on the cover by the wind, a large number of ballast weights, such as automobile tires, were attached to the cover at fixed attachment points so that the ballast weights rested on the cover between the top or apex and the lower margin of the pile. However, if the pile had an atypical size or shape or as particulate matter was removed from the pile and the height of the pile diminished, the fixed attachment points ended up so close to the ground that the ballast weights rested on the ground which reduced or eliminated the effectiveness of the weights in maintaining the cover on the pile.
The wind may also enter beneath the cover through a removal opening or otherwise get beneath the cover and exert tensile forces on the cover. The prior Handwerker cover included canvas panels which were porous to gas which allowed the cover to breathe and reduce the stress exerted by the wind on the cover. In addition, the canvas material would form rips if the stress became too great. However, once a canvas panel formed a rip, the rip had a tendency to propagate and extend the entire length of the panel, resulting in a substantial cost to repair the rip. Such ripping may also occur in polyethylene panels of a cover under certain stress conditions.
Thus there is a need for a cover for a pile of particulate material which protects the pile from the elements and resists the effects of wind on the cover. A related need is for a cover which allows for the attachment of ballast weights at desired locations on the cover and also allows for each ballast attachment point to be shifted to compensate for changes in the shape and height of the pile.
There is a further need for a cover for a pile of particulate material which prevents rips which may form in the panels compromising the cover from propagating for more than a desired short length that is easy to repair.